Playback devices, such as laptop computers, cellular radiotelephones, portable music players, and televisions, include amplifiers and audio transducers (e.g., loudspeakers) with limited output capabilities. In such devices, audio playback is perceptibly distorted, and often acutely distorted, as playback level is increased during presentation. Further, this distortion is oftentimes frequency dependent for a playback device. For example, a television's form factor may exhibit a resonance response at a specific frequency when an output signal generally exceeds a particular level, resulting in an annoying rattle.
Multi-band compression can be applied to the audio signal prior to playback to reduce distortion and attempt to maximize playback level. A distortion threshold is specified for each frequency band of the compressor. The compressor independently applies differing gain values to each frequency band to ensure an output signal does not exceed any of the corresponding distortion thresholds.
However, this approach can drastically alter timbre, or an attribute of listener perception where two sounds of equal loudness and pitch can be perceived as dissimilar. That is to say, when certain frequencies reach a distortion threshold and others do not, the compressor introduces its own disadvantages by altering relative balance amongst these frequencies. Each band operates in isolation. The resulting sound emerges as aberrant, or otherwise unnatural.
From the above, it is appreciated by the inventor that techniques for timbre preservation with multi-band compression is desirable for a decidedly natural hearing experience.
The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section. Similarly, issues identified with respect to one or more approaches should not assume to have been recognized in any prior art on the basis of this section, unless otherwise indicated.